Question

我在viewWillAppear中写了一个订阅但它也在首次启动应用程序中运行一次当我推送到另一个viewcontroller时，我使用dispose（）。
然后我回到第一个viewcontroller，我的订阅功能在viewWillAppear中运行。
我的rx订阅有什么问题？

var listSubscribe:Disposable?

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    listSubscribe = chatrooms.notifySubject.subscribe({ json in
        print("*1") //just print once in first launch
        self.loadContents()
    })
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)

    let controllers = tabBarController?.navigationController?.viewControllers
    if (controllers?.count)! > 1 {
        listSubscribe?.dispose()
    }
}

Answer 1

RxSwift文档说"Note that you usually do not want to manually call dispose; this is only an educational example. Calling dispose manually is usually a bad code smell."

通常，你应该做这样的事情 -

    let disposeBag = DisposeBag()

    override func viewDidLoad() {
        super.viewDidLoad()

        whatever.subscribe(onNext: { event in
        // do stuff
        }).disposed(by: self.disposeBag)

    }

至于你的问题，我相信你不需要重新订阅，因为你的订阅将会存在并且“通知主题”。只要有任何更新，我们都会向您发送更新。

Answer 2

也许你可以获得viewWillAppear和类似功能的反应性实现？并忘记手动一次性用品处理...例如，您的UIViewController init将包含以下内容：

rx.driverViewState()
    .asObservable()
    .filter({ $0 == .willAppear })
    .take(1) // if you need only first viewWillAppear call
    .flatMapLatest({ _ in
        // Do what you need
    })

driverViewState的实施：

public extension UIViewController {

    public enum ViewState {
        case unknown, didAppear, didDisappear, willAppear, willDisappear
    }
}

public extension Reactive where Base: UIViewController {

    private typealias _StateSelector = (Selector, UIViewController.ViewState)
    private typealias _State = UIViewController.ViewState

    private func observableAppearance(_ selector: Selector, state: _State) -> Observable<UIViewController.ViewState> {
        return (base as UIViewController).rx
            .methodInvoked(selector)
            .map { _ in state }
    }

    func driverViewState() -> Driver<UIViewController.ViewState> {
        let statesAndSelectors: [_StateSelector] = [
            (#selector(UIViewController.viewDidAppear(_:)), .didAppear),
            (#selector(UIViewController.viewDidDisappear(_:)), .didDisappear),
            (#selector(UIViewController.viewWillAppear(_:)), .willAppear),
            (#selector(UIViewController.viewWillDisappear(_:)), .willDisappear)
        ]
        let observables = statesAndSelectors
            .map({ observableAppearance($0.0, state: $0.1) })
        return Observable
            .from(observables)
            .merge()
            .asDriver(onErrorJustReturn: UIViewController.ViewState.unknown)
            .startWith(UIViewController.ViewState.unknown)
            .distinctUntilChanged()
    }
}

为什么RxSwift订阅只在第一次启动viewWillAppear中运行一次？

2 个答案: